Dear Larry,

Thanks for your very prompt reply.

Apologies for leaving out certain crucial info, here they are:

1. No conversion at all. Was using R12 previously, and still is using R12 now.

2. As far as I see it, there's no leak whatsoever anywhere in the a/c system.

3. Sorry but what is meant by "evacuating and charging" the system? If charging refers to topping up with R12 gas, then I had that done.

4. The hoses were left open for about 45mins while the compressor and clutch were being replaced.

With these additional info, would your advice still be the same?
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Summary; if there are no leaks and you are staying with R12 and have yet to evacuate the system, I suggest you replace the filter/drier, pump down, ensure that it will hold the vacuum for several minutes(gross leak check) then charge the system.
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Thanks again Larry!

Mervyn
1983 W126 (280SEL)